Activity of cortical neurons and hippocampal CA 1 neurons was recorded during 5 minute forebrain ischemia and following recirculation in gerbils. Spontaneous activity in both cortical and CA1 neurons ceased to appear within 60 sec of the onset of ischemia and it began to reappear 10-20 min after recirculation. Furthermore, during 24 hours a considerable number of CA1 neurons showed hyperactivity as shown by an increase in spike discharges. However, on the second day of ischemia CA1 neurons became completely silent, although histological sections showed a relatively good preservation of their cellular structure. These findings indicate that recovery of neuronal activity after an ischemic insult may still be followed by neuronal death, as late as 3 days after recirculation. Also, these studies show that functional neuronal death may be associated with good structural preservation of the neurons.